At present there are many known and widely-used techniques for heating a food product, both for thawing and for cooking.
According to some known heating techniques, the food product receives heat through its outer surface, which exchanges heat with an external heating element or with an external environment which is at a higher temperature. In these techniques, the flow of heat inside the food product is determined by the temperature gradient and by thermal diffusivity of the food product itself.
According to other known heating techniques, heat is generated directly inside the food product by means of electromagnetic fields or electromagnetic radiations. Amongst these, some techniques use radio frequency (RF) dielectric heating and other techniques use microwaves (MW). Conventionally, radio frequency (RF) electromagnetic waves lie within the band of frequencies between 1 and 300 MHz, whilst microwaves (MW) lie within the band of frequencies between 300 MHz and 300 GHz. Generally speaking, radio frequency heating devices and microwave heating devices are known and widely utilized.
Electromagnetic heating techniques that use radio frequency or microwaves are generally useful for achieving shorter thawing or cooking times than techniques that use heat exchange through the surface of the food product. However, a problem common to many known electromagnetic heating techniques relates to the difficulty of performing heating of a specific load of product in a reproducible, efficient manner or complying with other user requirements. That problem normally seems to be more significant for microwave heating devices.
It should be considered that each product has an individual, specific manner to interact with microwaves in a heating chamber of a microwave heating device. Thus, a same operational configuration in terms of frequency and phase shifts of the microwaves may result in efficiency values that are remarkably different from one another when applied to different products to be heated. A similar remark can be made also when spatial uniformity of heating is taken into account. Consequently, when a same operational configuration of the microwave heating device is used for heating different products, it may be found that those products are poorly heated, or overheated or not uniformly heated.
In some prior-art microwave heating devices, cooking recipes are memorized for some product types and can be selected by the user. However, each recipe is based on the behavior of an average product and then its use may result unsatisfactory for an actual load of product.
Moreover, it should be considered that a different positioning of a same product in a microwave heating device may entail a different interaction with microwaves and then a different heating of the product. Therefore, a wrong positioning of the product may reduce the performance of a memorized recipe for that product.
Therefore, it would be desirable to have available a method for operating a heating device, in particular using microwaves, that may be adapted to a specific load of product.